Engineering topics

Ohishi, M.

Publications and source records attributed to Ohishi, M..

8 records

NASA NTRS2001

Searches for new interstellar molecules, including a tentative detection of aziridine and a possible detection of propenal

Rotational spectroscopy at millimeter wavelengths is a powerful means of investigating the chemistry of dense interstellar clouds. These regions can exhibit an interesting complement of gas phase molecules, including relatively complex organics. Here we report the tentative first astronomical detection of aziridine (ethylenimine), the possible detection of propenal (acrolein), and upper limits on the abundances of cyclopropenone, furan, hydroxyethanal (glycolaldehyde), thiohydroxylamine (NH2SH), and ethenol (vinyl alcohol) in various interstellar clouds.

Acrolein/analysis↗

NASA NTRS1998

Abundances of ethylene oxide and acetaldehyde in hot molecular cloud cores

We have searched for millimetre-wave line emission from ethylene oxide (c-C2H4O) and its structural isomer acetaldehyde (CH3CHO) in 11 molecular clouds using SEST. Ethylene oxide and acetaldehyde were detected through multiple lines in the hot cores NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2. Acetaldehyde was also detected towards G10.47+0.03, G322.2+0.6, and Orion 3'N, and one ethylene oxide line was tentatively detected in G10.47+0.03. Column densities and rotational excitation temperatures were derived using a procedure which fits the observed line intensifies by finding the minimum chi 2-value. The resulting rotational excitation temperatures of ethylene oxide and acetaldehyde are in the range 16-38 K, indicating that these species are excited in the outer, cooler parts of the hot cores or that the excitation is significantly subthermal. For an assumed source size of 20", the deduced column densities are (0.6-1)x10(14) cm-2 for ethylene oxide and (2-5)x10(14) cm-2 for acetaldehyde. The fractional abundances with respect to H2 are X[c-C2H4O]=(2-6)xl0(-10), and X[CH3CHO]=(0.8-3)x10(-9). The ratio X[CH3CHO]/X[c-C2H4O] varies between 2.6 (NGC 6334F) and 8.5 (G327.3-0.6). We also detected and analysed multiple transitions of CH3OH, CH3OCH3, C2H5OH, and HCOOH. The chemical, and possibly evolutionary, states of NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2 seem to be very similar.

Non-NASA Center↗

NASA NTRS1997

Hydrogenation of interstellar molecules: a survey for methylenimine (CH2NH)

Methylenimine (CH2NH) has been convincingly detected for the first time outside the Galactic center as part of a study of the hydrogenation of interstellar molecules. We have observed transitions from energy levels up to about 100 K above the ground state in the giant molecular clouds W51, Orion KL and G34.3 + 0.15. In addition, CH2NH was found at the " radical-ion peak" on the quiescent ridge of material in the Orion molecular cloud. The abundance ratio CH2NH/HCN at the radical-ion peak agrees with the predictions of recent gas-phase chemical models. This ratio is an order of magnitude higher in the warmer cloud cores, suggesting additional production pathways for CH2NH, probably on interstellar grains.

Non-NASA Center↗

NASA NTRS1996

A Search for Interstellar Oxiranecarbonitrile (C3H3NO)

We report a search in cold, quiescent and in 'hot core' type interstellar molecular clouds for the small cyclic molecule oxiranecarbonitrile (C3H3NO), which has been suggested as a precursor of important prebiotic molecules. We have determined upper limits to the column density and fractional abundance for the observed sources and find that, typically, the fractional abundance by number relative to molecular hydrogen Of C3H3NO is less than a few times 10(exp -10). This limit is one to two orders of magnitude less than the measured abundance of such similarly complex species as CH3CH2CN and HCOOCH3 in well-studied hot cores. A number of astrochemical discoveries were made, including the first detection of the species CH3CH2CN in the massive star-forming clouds G34.3+0.2 and W51M and the first astronomical detections of some eight rotational transitions of CH3CH2CN, CH3CCH, and HCOOCH3. In addition, we found 8 emission lines in the 89 GHz region and 18 in the 102 GHz region which we were unable to assign.

Dicken, J. E.↗

NASA NTRS1993

Interferometric observations for oxygen-containing organic molecules toward Orion-KL

High spatial resolution observations were made for the 3 mm transitions of methanol (CH3OH), methyl formate (HCOOCH3), and dimethyl ether (/CH3/2O) toward Orion-KL using the Nobeyama Millimeter Array. The 15(3)-14(4) A(-) CH3OH emission appears to be elongated along the line connecting IRc2 and 'the southern condensation (SC)', which may suggest a relation between methanol and the outflow from IRc2. The HCOOCH3 (7(1,6)-6(1,5)) and (CH3)2O (15(2,13)-15(1,14)) emissions appear to be well concentrated toward SC with an angular size of about 6.5 arcsec. There also exists another oxygen-rich condensation to the west of IRc2 having column densities of HCOOCH3 and (CH3)2O comparable to those of SC. We derive the total column densities 6.8 x 10 exp 16/sq cm, 1.4 x 10 exp 16/sq cm, and 2.7 x 10 exp 16/sq cm for CH3OH, HCOOCH3, and (CH3)2O, respectively, at the core of SC.

Minh, Y. C.↗

NASA NTRS1993

Measurement of the methyl cyanide E/A ratio in TMC-1

We have observed the methyl cyanide (CH3CN) J = 2-1 K = 0 and 1 transitions toward the cyanopolyyne peak of TMC-1 and have derived an E/A (ortho/para)abundance ratio N(E)/N(A) = 0.75 +/- 0.10. The total methyl cyanide column density is N(total) = 5 x 10 exp 12/sq cm toward TMC-1, in agreement with earlier results from the J = 1-0 lines.

Minh, Y. C.↗

NASA NTRS1992

Recent observations of interstellar molecules - Detection of CCO and a limit on H2C3O

In order to test gas-phase reaction schemes for the production of small oxides of carbon in cold, dense interstellar clouds, we have searched for the radical CCO and for propadienone (H2C3O) in Taurus Molecular Cloud 1, a nearby cloud which exhibits a rich organic chemistry. The radical CCO has been detected with a fractional abundance some two orders of magnitude less than that of CCS, about one order of magnitude less than that of H2CCO, and slightly less than that of C3O. An upper limit has been obtained on the abundance of propadienone which is slightly less than that of its isomer propynal (HC2CHO).

Brown, R. D.↗

NASA NTRS1985

Recent observations of organic molecules in nearby cold, dark interstellar clouds

Recent investigations of the organic chemistry of relatively nearby cold, dark interstellar clouds are reported. Specifically, the presence of interstellar tricarbon monoxide (C3O) in Taurus Molecular Cloud 1 (TMC-1) is confirmed. The first detection in such regions of acetaldehyde (CH3CHO), the most complex oxygen-containing organic molecule yet found in dark clouds is reported, as well as the first astronomical detection of several molecular rotational transitions, including the J = 18-17 and 14-13 transitions of cyanodiacetylene (HC5N), the 1(01)-0(00) transition of acetaldehyde, and the J = 5-4 transition of C3O. A significant upper limit is set on the abundance of cyanocarbene (HCCN) as a result of the first reported interstellar search for this molecule.

Suzuki, H.↗